A gas chromatographic-mass spectrometric study of organic metabolites excreted in urine by normal infants will be the basis for a study of subtle metabolic disorders which do not alter metabolic profiles as dramatically as gross enzyme deficiencies. This program is being pursued in parallel with a metabolic screening program for inborn errors of metabolism. Structure identifications by gas chromatography- mass spectrometry-computer techniques will be followed by quantitative determination for individual metabolites. Organic acids will be studied first, followed by bases and neutrals. A second study on structure determination of glycosphingolipids by chemical ionization and field desorption mass spectrometry is a part of the effort to bring the latest mass spectral methods to bear on clinical and biochemical research. Computer programming to automate m/e scale identification of spectra produced by chemical ionization and field desorption, and construction of a field desorption ionization source are portions of the proposed research.